The invention relates to a process for producing a commutator, especially a flat commutator, for electrical machinery according to the preamble of patent claim 1.
DE 41 40 475 C2 discloses a process for producing a molded material flat commutator of the aforementioned type. In this case an essentially unmachined raw conductive material is used, preferably in the form of rod material, from which an initial body for example in the form of a round is cut. By means of extrusion this base body is formed into a pot-shaped blank, which has a circular ring-shaped flat part and a tubular jacket adjoining it. In the course of multistage forming inner anchoring elements and outer anchoring elements arranged like a collar are shaped to later reliably anchor to the commutator the molding material which is to be held in the pot-shaped interior of the blank and which is used as the insulating mass. At a later station an annular flange which projects radially to the outside is molded onto the free end of the jacket of the pot-shaped blank by displacement of material in the axial direction against the free end of the jacket. At a further station lug-shaped connection elements are obtained by punching out of the annular flange shaped beforehand. In this punching process the outer anchoring elements are also separated. By punching the connection elements out of the annular flange shaped continuously beforehand, on the free end of the jacket of the blank scrap material results which remains unused, especially the remaining and punched-out connection elements taking only a small fraction of the overall annular flange surface, so that a relatively large amount of material is lost in this production.
Another problem lies in that during the various extrusion treatments and also in the formation of the annular flange material hardening is necessarily caused by the forming so that the connection elements formed are less ductile or bendable than the initial raw material. After completion of the commutator however connecting leads are wound around these connection elements and then the connection elements are bent back onto the outside of the cylindrical jacket. As a result of material embrittlement therefore cracks have occurred in the conventional manner of production and they must generally be expected. The known production process also comprises a host of individual deformation steps, from which an economical method of production of these commutators suffers.
U.S. Pat. No. 3,812,576 whose defects and difficulties will be surmounted with the above discussed DE 41 40 475 C2 discloses a process for producing a commutator for electrical machinery in which, proceeding from a disk-shaped conductive raw material, a cylindrical part is produced which has one open end with a continuous annular flange which projects radially to the outside, and a bottom. By means of pressing, the relieved parts from the interior of the cylindrical section of the cylindrical part are shaped and during subsequent addition of the insulation prevent the adhesion of the insulation to the annular flange or to the outer surface of the bottom. Then the annular flange is machined by punching such that lug-shaped connection elements therefrom remain and the relieved sections and the punched out parts of the annular flange are removed.
Aside from the large number of individual stations, when the lug-shaped connection elements are punched out scrap material results and the individual forming treatments engender the danger that material hardening or embrittlement will occur on the individual, lug-shaped connection elements obtained subsequently by punching out.